This invention relates to a label for use in in-mold decorating in which the label is set within a metal mold so that the printed surface of the label is in contact with the wall of the mold, and a thermoplastic resin parison is introduced into the mold in a molten state and blow-molded, or a molten thermoplastic resin sheet is vacuum-molded or air-pressure formed to produce a label-laminated container.
Conventionally, label-laminated resin containers produced by the one-piece molding of a resin have been made by inserting a blank or a label into a metal mold and forming a container within the metal mold by injection molding, blow-molding, differential pressure molding or foam molding (see Japanese Patent Laid-Open No. 69015/1983 and EP-A-254923). Gravure printed resin films or offset multi-color printed synthetic paper (for example, see Japanese Patent Publication No. 7814/1990 and Japanese Patent Laid-Open No. 84319/1990) or aluminum labels having an aluminum foil laminated on its back side in a high pressure process, low density polyethylene or ethylene/vinyl acetate copolymer sheets which are gravure printed on their surface are known as labels for such in-mold decorating.
However, in the process of producing label-laminated containers by in-mold decorating using a label or blank for in-mold decorating, has the problem that, especially in summer, the adhesive ingredients of such labels become so sticky due to the high temperature of summer, that the parting or sliding properties of the paper sheets deteriorates upon printing films or synthetic paper, particularly when using offset sheet printing, resulting in the need to stop and restart the label-producing machine many times.
Furthermore, when carrying out gravure printing or flexographic printing using rolls, the sheets have to be stopped during the sheeting step, after printing, due to the irregular position of the paper caused by the poor sliding properties of the printed paper.
In addition, during transportation of packed printed or blanked labels, the labels are liable to adhere to each other, or cause blocking in the high temperature environment and, upon feeding the labels into a metal mold using an automatic label-feeding apparatus, for example in the in-mold decorating process, two or more labels may be fed at the same time into the metal mold, resulting in production of containers having labels at an undesirable position (defective labels), as well as ineffective utilization of the labels.
An object of the present invention is to provide a label for use in in-mold decorating, which shows excellent blocking resistance even under the high temperature environment of summer, shows good working properties, and to provide a container wherein the label is strongly welded to the container.
The present invention is a label for use in in-mold decorating, which is characterized in that it comprises a thermoplastic, resin film substrate layer (I) which has on its backside a heat-sealable resin layer (II). The resin base material of this heat-sealable resin layer (II) comprises a polyethylenic resin containing least one of (i) a fatty acid amide having a molecular weight of 300 or more and (ii), an organic or inorganic fine powder having an average particle size larger than thickness of the heat-sealable resin layer (II).
By incorporating into the polyethylenic resin of the heat-sealable resin layer (II) at least one of the above-described fatty acid amides and organic or inorganic fine powder, the feeding and discharging properties of the labels after printing, or the arranging properties of the labels upon sheeting are improved, errors upon insertion of the label into the metal mold are decreased, and the welded bonding of the label to a container body after in-mold decorating is strengthened.